An on-board charger (OBC) of an electric vehicle is used for charging a traction battery of the vehicle. The OBC charges the battery with electrical power from a mains supply. The electrical power from the mains supply is an AC electrical power. The battery is to be charged with DC electrical power. The OBC has an input which connects to the mains supply for the OBC to receive AC electrical power from the mains supply. The OBC converts AC electrical power received from the mains supply into DC electrical power. The OBC has an output which connects to the battery. The OBC provides the DC electrical power converted from the AC electrical power to the battery for charging the battery.
The OBC has one or more internal bulk capacitors (collectively “DC link capacitor”). The DC link capacitor is charged with the DC electrical power converted from the AC electrical power to have a DC voltage (“DC-link voltage”). In a stable operation mode of the OBC, the DC link voltage is a boosted, constant DC voltage. The DC link capacitor is connected to the traction battery through a DC/DC converter and, typically, a disconnection switch. The DC/DC converter is used for voltage adaption as the traction battery voltage could vary in a relatively wide range (for instance, 200V-400V) while the DC-link voltage is expected to be constant.
In a pre-charge operation mode of the OBC, the DC link capacitor is to be charged to the boosted, constant DC voltage. At the beginning of the pre-charge operation the DC link voltage is zero volts or a low voltage (i.e., the DC link capacitor is discharged or nearly discharged). The DC link capacitor is to be progressively charged so that inrush electrical currents are avoided. Inrush electrical currents could damage internal components of the OBC or the mains supply.